JP2604839Y2 - Ceramic filter - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy trapping type ceramic filter used, for example, as an intermediate frequency filter of an FM tuner. More specifically, the present invention relates to an insertion loss without securing mechanical strength and without deteriorating characteristics. The present invention relates to an improvement of a ceramic filter which can reduce the amount of attenuation and increase the amount of out-of-band attenuation.

[0002]

2. Description of the Related Art This type of ceramic filter has a plurality of energy trapping type vibrating parts on the same piezoelectric substrate at intervals, as is known from publicly known documents such as Japanese Utility Model Laid-Open No. 57-2727. It has the basic structure arranged. Due to this basic structure, mechanical interference occurs between the vibrating parts, and spurs are generated. Conventionally, as means for reducing spurious, a mass load is applied by attaching solder or the like to a vibrating electrode, and the damping action is used, or a slit is provided between vibrating parts as described in the above-mentioned known document. And so on.

[0003]

However, in a structure in which a mass load is applied to the vibrating electrode, the polarization under the vibrating electrode disappears due to the influence of heat during soldering when the solder serving as the mass load is attached. Problems such as deterioration of characteristics and an increase in insertion loss occur.

In the structure in which the slit is provided, if the slit is too deep, the mechanical strength of the piezoelectric substrate is reduced, and if the slit is too shallow, a sufficient spurious reduction effect cannot be obtained. The above-mentioned known documents do not disclose the condition of the slit for securing the mechanical strength and reducing the spurious.

[0005] Therefore, an object of the present invention is to solve the above-mentioned conventional problems, to secure mechanical strength, reduce insertion loss and increase out-of-band attenuation without deteriorating characteristics. It is to provide a ceramic filter.

[0006]

In order to solve the above-mentioned problems, a ceramic filter according to the present invention comprises a piezoelectric substrate.
And, look including a plurality of energy-trap type vibration unit, M
It is used in a frequency range of not less than Hz. The piezoelectric substrate,
It has a substantially rectangular plate shape and is made of a piezoelectric ceramic material.
The plurality of energy trapping type vibrating portions have vibrating electrodes overlapping on the front and back of the piezoelectric substrate, and are arranged at intervals in the length direction X of the piezoelectric substrate. Previous
The piezoelectric substrate further has a slit between the vibrating portions.
You. The slit is provided from one edge in the width direction Y of the piezoelectric substrate toward the center, and the width of the piezoelectric substrate is H, and the width of the vibrating electrode taken in the width direction Y from the one edge of the piezoelectric substrate is H. Assuming that the distance to the farthest end of the overlapping portion is C, the depth D in the width direction Y satisfies C ≦ D ≦ H / 2. Each of the vibrating portions, on the one surface,
It has two drive electrodes facing each other at an interval in the width direction Y. Here, a center line extending in the width direction Y by substantially dividing the length dimension of the drive electrode into two, and a center line extending in the length direction X by substantially dividing the distance between the two drive electrodes into two The point of intersection with the minute is defined as the center of vibration. Among the plurality of vibrating parts,
A distance in the length direction X between the vibration centers of two vibrating portions adjacent to each other via the slit is defined as A (mm). Further, among the plurality of vibrating portions, a length direction X
For one of the two outermost vibrating portions, the distance from the vibration center to one end of the piezoelectric substrate positioned on one side in the length direction X is B1 (mm), and the width from the vibration center is B1 (mm). The distance from one end of the piezoelectric substrate located on one side in the direction Y is B2 (mm), and the distance from the vibration center to the other end of the piezoelectric substrate located on the other side in the width direction Y is B3 ( mm). Further, for the other of the two vibrating portions located on both outermost sides in the length direction X, the distance from the center of the vibration to the other end of the piezoelectric substrate located on the other side in the length direction X is B1 (mm). ), The distance from the vibration center to one end of the piezoelectric substrate located on one side in the width direction Y is B2 (mm), and the other of the piezoelectric substrate located on the other side in the width direction Y from the vibration center The distance to the edge is B3 (mm). Further, for each of two vibrating portions adjacent via the slit, the distance from the respective vibration center to the edge of the slit is represented by B
4 (mm). Under the conditions described above, A ≧ 1 for the propagation wavelength λ (mm) in the substrate in the operation vibration mode.
0λ, B1 ≧ 1.5λ, B2 ≧ 1.5λ, B3 ≧ 1.5
λ, B4 ≧ 1.5λ. In the following description, the distances B1, B2, B3, and B4 may be described as Bn (n = 1 to 4). In the distance Bn (n = 1 to 4), n = 1 means the distance B1, n = 2 means the distance B2, n = 3 means the distance B3, and n = 4 means the distance B4.

[0007]

[Function] Since a plurality of energy trapping type vibrating parts are provided on the same piezoelectric substrate and the piezoelectric substrate has slits between the vibrating parts, the slits prevent mechanical interference between the vibrating parts and reduce spurious. it can.

The vibrating portion has vibrating electrodes overlapping on the front and back of the piezoelectric substrate, and is arranged at intervals in the longitudinal direction of the piezoelectric substrate. The slit extends from one edge in the width direction of the piezoelectric substrate toward the center. When the width of the piezoelectric substrate is H, and the distance from one edge of the piezoelectric substrate to the farthest end of the overlapping portion of the vibrating electrodes taken in the width direction is C,
Since the depth D in the width direction satisfies C ≦ D and (H−D) ≧ 0.7λ , it is necessary to secure the mechanical strength of the piezoelectric substrate, reduce spurious, and increase the out-of-band attenuation. Can be.

In addition, the propagation wavelength in the substrate in the operation vibration mode is λ, and the distance from the vibration center of the vibration part to the edge of the substrate is
When B _n (n = 1 to 4) , the distance B _n (n = 1 to 4)
Satisfy B _n (n = 1 to 4) ≧ 1.5λ, the insertion loss can be reduced.

[0010] The above-described operation is achieved by the depth D and the distance of the slit.
It is obtained by selecting B _n (n = 1 to 4) . Therefore, unlike the prior art in which a mass load is applied by attaching solder or the like to the vibrating electrode and the spurious is reduced by the damping action, there is no deterioration in characteristics.

[0011]

1 is a plan view of a ceramic filter according to the present invention, and FIG. 2 is a bottom view of the ceramic filter shown in FIG. On one surface of the same piezoelectric substrate 1, there are two energy trapping type vibrating parts 2, 3. The invention is ceramic
The piezoelectric substrate 1 is a piezoelectric ceramic
It is obvious that it is made of a mic material. The piezoelectric substrate 1 is a rectangular flat plate having a length L and a width H. The distance between the centers O1 and O2 of the two adjacent vibrating portions 2 and 3 is A, and the center O1 of the vibrating portions 2 and 3 is O1. , O2 to the four edges 11, 12, 13, and 14 of the piezoelectric substrate 1 are B1, B2, B3, and B4, and when the propagation wavelength in the substrate in the operation vibration mode is λ, the distance A and the distance Bn (N = 1
4) is A ≧ 10λ, Bn (n = 1 to 4) ≧ 1.5λ
Meet. The meaning of the distance Bn (n = 1 to 4) is as described above. More specifically, the energy confinement type vibrating parts 2 and 3 are composed of a piezoelectric substrate
1 are arranged at a distance in the longitudinal direction X. The vibrating part 2 has an interval g in the width direction Y on one surface of the piezoelectric substrate 1.
It has two drive electrodes 21 and 22 facing each other with 1 therebetween. The vibrating part 3 includes two drive electrodes 31, 3 opposed on one surface of the piezoelectric substrate 1 at an interval g2 in the width direction Y.
2 Here, the vibration center O1 is
At the intersection of the center line extending in the width direction Y by dividing the length dimension of the drive electrode 22 by approximately 2 and the center line extending in the length direction X by dividing the distance g1 between the drive electrodes 21 and 22 by approximately 2 Given.
The vibration center O2 has a length dimension of the drive electrodes 31 and 32 of approximately 2
A center line segment extending in the width direction Y and driving electrodes 31 and 3
2 is given by the intersection with the center line extending in the length direction X by substantially dividing the interval g2 between the two. The distance A (mm) is the distance in the length direction X between the vibration centers O1 and O2 of the two adjacent vibration parts 2 and 3. Distances B1, B2 and B3
Are two vibrating parts 2 located on both outermost sides in the length direction X,
3, given by the distance between each vibration center O 1 or O 2 and the edge of the piezoelectric substrate 1. First,
In the vibrating part 2, the distance B1 (mm) is equal to one edge 1 of the piezoelectric substrate 1 located on one side in the length direction X from the vibration center O1.
The distance to 1. Further, the distance B2 (mm) is a distance from the vibration center O1 to one end edge 14 of the piezoelectric substrate 1 located on one side in the width direction Y. Further, the distance B3 (mm) is a distance from the vibration center O1 to the other end 12 of the piezoelectric substrate 1 located on the other side in the width direction Y. In the vibration part 3,
The distance B1 (mm) is a distance from the vibration center O2 to the other end 13 of the piezoelectric substrate 1 located on the other side in the length direction X. The distance B2 (mm) is a distance from the vibration center O2 to one edge 14 of the piezoelectric substrate 1 located on one side in the width direction Y. Further, the distance B3 (mm) is a distance from the vibration center O2 to the other end 12 of the piezoelectric substrate 1 located on the other side in the width direction Y. The distance B4 (mm) is given by the distance from each of the vibration centers O1 and O2 to the edge of the slit 10 for each of the two vibrating portions 2 and 3 adjacent to each other via the slit 10. First, in the vibrating part 2, the distance B4 (mm) is the distance between the vibration center O1 and the edge 102 of the slit 10. In the vibrating section 3, the distance B 4 (mm) is the center of vibration O 2 and the edge 1 of the slit 10.
03.

The vibrating portions 2 and 3 have vibrating electrodes (21 and 22) and a vibrating electrode 25, vibrating electrodes (31 and 32) and a vibrating electrode 35 overlapping on the front and back of the piezoelectric substrate 1, respectively. The slit 10 is provided from the one edge 14 in the width direction of the piezoelectric substrate 1 toward the center. The width of the piezoelectric substrate 1 is set to H, and the vibration electrode 2 taken in the width direction from the one edge 14 of the piezoelectric substrate 1.
Assuming that the distance to the farthest end of the overlapping portion 3 is C, the depth D in the width direction is C ≦ D and (HD) ≧ 0.7λ.
Meets. The depth D is a dimension from one edge 14 of the piezoelectric substrate 1 to the bottom 101 of the slit 10. Bottom 10
The position of 1 satisfies C ≦ D and (HD) ≧ 0.7λ.
D is set in the range. If the depth D is smaller than the distance C, a sufficient spurious reduction effect by the slit 10 cannot be obtained. When (HD) becomes smaller than 0.7λ , the mechanical strength of the piezoelectric substrate 1 decreases, and as shown in FIG.
Then, the defective rate rises sharply. In the present invention, since the depth D in the width direction satisfies C ≦ D and (HD) ≧ 0.7λ , the mechanical strength of the piezoelectric substrate is secured, spurious is reduced, and the out-of-band attenuation is reduced. Can be greatly increased.

FIG. 3 shows a structure 1 having the structure shown in FIGS.
It is a figure which shows the attenuation characteristic and insertion loss characteristic of a 0.7 MHz ceramic filter. The horizontal axis shows two scales of ( CD ) / λ and (CD) mm, the left vertical axis shows out-of-band attenuation (dB), and the right vertical axis shows insertion loss (dB). is there. λ is the propagation wavelength in the substrate in the operation vibration mode, which is 0.42 mm at 10.7 MHz. Characteristic L1
Is an out-of-band attenuation characteristic, and L2 is an insertion loss characteristic. As shown in FIG. 3, an out-of-band attenuation of about 45 (dB) can be secured in the region of C ≦ D with the vicinity of CD = 0 as a boundary.
Moreover, the insertion loss has hardly increased. On the other hand, in the region of C> D, the out-of-band attenuation decreases linearly.

Next, when the propagation wavelength in the substrate in the operation vibration mode is λ, and the distance from the vibration centers O1 and O2 of the vibrating parts 2 and 3 to the edge of the substrate is B _n (n = 1 to 4) , Distance B _n
(N = 1 to 4) satisfies B _n (n = 1 to 4) ≧ 1.5λ. With such a structure, the amount of out-of-band attenuation can be increased without increasing insertion loss. FIG. 4 is a characteristic diagram showing a relationship between the distance B and the insertion loss (dB).
In FIG. 4, two scale axes are plotted on the horizontal axis, and the attenuation (dB) is plotted on the vertical axis. The first horizontal axis (upper side) is a scale on which the distance B _n (n = 1 to 4) is indicated by the propagation wavelength λ in the substrate, and the second axis (lower side) is the distance B _n (n
= 1 to 4) in actual dimensions (mm). As shown, the distance B _n (n = 1 to 4) is 1.5
Above λ, the insertion loss sharply drops.

In the embodiment, the piezoelectric substrate 1 is a rectangular flat plate having a length L and a width H, and the distance B1 is the distance from the edge 11 of the piezoelectric substrate 1 to the vibration center O1 of the vibration section 2.
Alternatively, it is the distance from the edge 13 of the piezoelectric substrate 1 to the vibration center O2 of the vibration part 3. The distance B2 is the edge 1 of the piezoelectric substrate 1.
4 is the distance from the vibration center O1 of the vibration part 2 or the vibration center O2 of the vibration part 3. The distance B3 is a distance from the edge 12 of the piezoelectric substrate 1 to the vibration center O1 of the vibration part 2 or the vibration center O2 of the vibration part 3. Distance B4 is slit 10
Or the distance from the edge 102 of the piezoelectric substrate 1 which is the inner edge to the vibration center O1 of the vibrating portion 2, or the distance from the edge 103 of the piezoelectric substrate 1 which is the inner edge of the slit 10 to the center O2 of the vibrating portion 3. Is the distance to

The distance A between the oscillation center O1 over O2 at two oscillating portions 2, 3 adjacent desirably set so as to satisfy Equation A ≧ 9 lambda. FIG. 5 is a diagram showing the relationship between the distance A and the amount of attenuation. In FIG. 5, two scale axes are plotted on the horizontal axis, and the attenuation (dB) is plotted on the vertical axis. The first horizontal axis (upper side) is a scale on which the distance A is displayed by the propagation wavelength λ in the substrate, and the second axis (lower side) is a scale on which the distance A is displayed in actual dimensions (mm). The symbol “△” in the figure indicates the characteristics of a conventional product in which solder is attached to the vibrating electrode to obtain a damping action by a mass load. As shown
If the distance A is equal to or greater than 9 lambda, than in the case of solder deposit damping it is conventional, it is possible to obtain a large out-of-band attenuation.

Referring again to FIG. 1 and FIG.
Has drive electrodes 21 and 22 arranged on one surface of the piezoelectric substrate 1 at a distance g1 in the direction of the width H. Drive electrode 2
Reference numeral 1 denotes a lead electrode 23 which is electrically connected to a connection electrode 24 provided at a corner where the edges 11 and 12 of the piezoelectric substrate 1 intersect. The drive electrode 22 is guided from the center of the piezoelectric substrate 1 by the lead electrode 27, and is connected to the capacitor electrode 41 provided at the center at the edge 12 of the piezoelectric substrate 1. The vibrating part 3 has symmetry with the vibrating electrode 2 and has drive electrodes 31 and 32 arranged on one surface of the piezoelectric substrate 1 with a gap g2 in the direction of the width H. The drive electrode 31 is electrically connected to a connection electrode 34 provided at a corner where the edges 13 and 12 of the piezoelectric substrate 1 intersect by a lead electrode 33. The drive electrode 32 is connected to the piezoelectric substrate 1 by the lead electrode 37.
And at the edge 12 of the piezoelectric substrate 1,
It is connected to a capacitor electrode 41 provided at the center.

The vibrating section 2 further has a common electrode 35 formed on the other surface opposite to the piezoelectric substrate 1 at a position facing the drive electrodes 21 and 22. The common electrode 35 is electrically connected to the ground electrode 42 provided at a position facing the capacitor electrode 41 by the lead electrode 26. Similarly, the vibrating section 3 also has a common electrode 35 formed at a position facing the drive electrodes 31 and 32 on the other surface opposite to the piezoelectric substrate 1. The common electrode 35 is electrically connected to the ground electrode 42 by the lead electrode 36.

The connection electrodes 24 and 34 have lead terminals 5 and 6
Are fixed by soldering, respectively, and the ground electrode 42
The lead terminals 7 are fixed by means such as soldering. As a well-known product of the energy trapping type ceramic filter, as is well known, the vibrating parts 2, 3
Is formed so that a hollow portion is formed around the entire structure, and the insulating resin 8 is entirely covered.

Although a two-element type ceramic filter has been described above as an example, the present invention can be similarly applied to a three-element type or four-element type ceramic filter or a multi-stage ceramic filter.

[0021]

As described above, according to the present invention, the following effects can be obtained. (a) Providing a ceramic filter having a plurality of energy trapping type vibrating parts on the same piezoelectric substrate, and the piezoelectric substrate having slits between the vibrating parts, thereby reducing spurious and reducing out-of-band attenuation. it can. (b) The vibrating section has vibrating electrodes overlapping on the front and back of the piezoelectric substrate, and is arranged at intervals in the longitudinal direction of the piezoelectric substrate, and the slit extends from one edge in the width direction of the piezoelectric substrate toward the center. When the width of the piezoelectric substrate is H, and the distance from one edge of the piezoelectric substrate to the farthest end of the overlapping portion of the vibrating electrodes taken in the width direction is C, the depth D in the width direction is Since C ≦ D and (HD) ≧ 0.7λ are satisfied, it is possible to provide a ceramic filter capable of securing the mechanical strength of the piezoelectric substrate, reducing spurious, and obtaining a large out-of-band attenuation. (c) In the piezoelectric substrate, the propagation wavelength in the substrate in the operation vibration mode is λ, and the distance from the vibration center of the vibration part to the substrate edge is B.
_n (n = 1 to 4) , the distance B _n (n = 1 to 4) is
Since B _n (n = 1 to 4) ≧ 1.5λ is satisfied, a ceramic filter with small insertion loss can be provided. (d) The above operation is performed by the slit depth D and the distance B _n (n
= 1 to 4) , which is different from the prior art in which a mass load is applied by attaching solder or the like to the vibrating electrode and the spurious is reduced by the damping action.
It is possible to provide a ceramic filter that does not cause deterioration in characteristics.

[Brief description of the drawings]

FIG. 1 is a plan view of a ceramic filter according to the present invention.

2 is a back side view of the ceramic filter shown in FIG.

FIG. 3 shows a 10.7 MH having the structure shown in FIGS. 1 and 2
FIG. 7 is a diagram illustrating attenuation characteristics and insertion loss characteristics of a ceramic filter of z.

FIG. 4 is a characteristic diagram showing a relationship between a distance B _n (n = 1 to 4) and an insertion loss (dB).

FIG. 5 is a diagram illustrating a relationship between a distance A and an amount of attenuation.

FIG. 6 shows the defect rate and (HD) mm and λ (HD) mm.
FIG. 7 is a graph showing the relationship between

[Explanation of symbols]

Reference Signs List 1 piezoelectric substrate 10 slit 2, 3 vibrating portion H width of piezoelectric substrate C distance from one edge of piezoelectric substrate to farthest end of overlapping portion of vibrating electrode taken in width direction D depth of slit in width direction B _n (n = 1 to 4) Distance from center of vibration of vibrating part to edge of substrate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-53605 (JP, A) JP-A-62-58715 (JP, A) JP-A-61-133717 (JP, A) JP-A-56-1983 4915 (JP, A) JP-A-55-28663 (JP, A) JP-A-3-24721 (JP, U) JP-A-3-2742 (JP, U) JP-A-56-174226 (JP, U) 60-121327 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 9/00-9/215 H03H 9/54-9/60

Claims (1)

(57) [Scope of request for utility model registration] 1. A piezoelectric substrate comprising : a piezoelectric substrate; and a plurality of energy trapping type vibrating portions , wherein the piezoelectric substrate is used in a frequency range of MHz or more.
A piezoelectric filter, wherein the piezoelectric substrate has a substantially rectangular flat plate shape.
Made of a click material, said plurality of trapped energy vibration unit has a vibrating electrode overlapping the front and back of the piezoelectric substrate, are arranged at intervals in the length direction X of the piezoelectric substrate, the piezoelectric The substrate further has a slit between the vibrating parts.
The slit is provided from one end edge in the width direction Y of the piezoelectric substrate toward the center, and the width of the piezoelectric substrate is H, and the slit is taken in the width direction Y from the one end edge of the piezoelectric substrate. When the distance to the farthest end of the overlapping portion of the vibrating electrodes is C, the depth D in the width direction Y is C ≦ D ≦ H / 2.
Each of the vibrating portions has two drive electrodes on the one surface facing each other at an interval in the width direction Y, and divides a length dimension of the drive electrode into approximately two. An intersection of a center line extending in the width direction Y and the center line extending in the length direction X with the interval between the two drive electrodes substantially divided into two is set as a vibration center; , A length direction X between the vibration centers of two vibration portions adjacent to each other via the slit.
Is A (mm), and one of the two outermost vibrating portions in the longitudinal direction X of the plurality of vibrating portions is located on one side in the longitudinal direction X from the vibration center. The distance from the vibration substrate to one end of the piezoelectric substrate is B1 (mm), the distance from the vibration center to one end of the piezoelectric substrate positioned on one side in the width direction Y is B2 (mm), and the vibration center is From the other end of the piezoelectric substrate located on the other side in the width direction Y to B
The distance between the center of the vibration and the other end of the piezoelectric substrate located on the other side in the longitudinal direction X with respect to the other of the two vibrating portions located on both outermost sides in the longitudinal direction X Is B1 (mm)
The distance from the vibration center to one end of the piezoelectric substrate located on one side in the width direction Y is B2 (mm), and the other end of the piezoelectric substrate located on the other side in the width direction Y from the vibration center The distance to the edge is B3 (mm), and the distance from each of the vibration centers to the edge of the slit is B4 (mm) for each of the two vibrating parts adjacent via the slit. When the propagation wavelength in the substrate is λ (mm), distances A (mm), B1 (mm), B2 (mm), B3
(Mm) and B4 (mm) are ceramic filters satisfying A ≧ 10λ, B1 ≧ 1.5λ B2 ≧ 1.5λ B3 ≧ 1.5λ B4 ≧ 1.5λ.